Fluid-pressure operated tensiometer



1940- G. P. LESSMANN 2,189,609

FLUID-PRESSURE OPERATED TENSIOMETER Filed March 27, 1957 WlTN ESSES:

Ger/Zara P. Lassmamz.

4 2m %m I mm Feb. 6, .1940

PATENT OFFICE 2.189.609 FLUm-PBESSURE ornas'rnn TENsIo METER Gerhard P. Lessmann, Forest Hills, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 27, 1937, Serial No. 133,419

13 Claims.

My invention relates, generally, to tension control systems and, more particularly, to fluid-presterial which varies in accordance with the degreeof deflection of, the material between predetermined limits of movement. Compensation for variation in the degree of deflection of the material from its normal path of travel is provided by mountingthe idler roller on a bell crank device having an angle between its arms which causes the tensioning device to beself-compensating over a certain range of operation and permits a limited amount of movement of the idler roller resulting from variations in the length of material between roll stands without appreciably changing the tension on the material. The tension producing force is provided by mounting an adjustable weight on the horizontal arm of the bell crank lever, thereby causing the idler roller, which is carried 'by the other arm, to exert a predetermined force against the strip of material. However, devices of this type have been found to be relatively slow in action because of the inertia of the heavy weight required to produce the necessary force. Furthermore, it

is difficult to adjust the weight while the device is in operation and, therefore, impracticable to vary the'pressure on the material to control the tension while'a strip is passing through the rolls.

Accordingly, an object of my invention is to provide a tensiometer for maintaining a tension on a strip of translatory material which will respond quickly to changes in the length of the -material between the roll stands of a rolling mill.

Another object of my invention is to provide a tensiometer which may be readily adjusted to vary the tension on a strip of material while it is passing-through the roll stands.

A further object of my invention is to provide for regulating the pressure exerted by a tensiometer in a tension control system.

A more general object of my invention is to provide a tension control system which will be regulating valve.

simple and emcient in operation and which may be economically constructed and installed.

Other objects of my invention will be described fully hereinafter or will be apparent to those skilled in the art. 5

In accordance with one embodiment of my invention, which may be applied to a rolling mill where it is desired to control the tension on the material between any two roll stands, the material is subjected to a transverse force at a point 10 betweenthe roll stands by means of an idler roller which is mounted on one end of a bell crank lever having an angle between its arms whichcauses the tensioning device to be selfcompensating over a certain range of operation. 15 The other end of the lever arm is-attached to a fluid-pressure operated piston which raises the idler roller against the strip of material. The pressure in the cylinder housing thepiston is .regulated andkept constant ,by a fluid pressure 20 regulating valve of the spring-loaded diaphragm type. The pressure maintained by the valve can be varied by an electrically energized solenoid disposed to counteract the spring in the The current in the solenoid 26 may be controlled manually by means of a rheostat, or automatically by means of a vibrating or other suitable regulator.

For a fuller understanding of the nature and objects of my invention, reference may be had 30 to the following detailed description, taken in conjunction with the accompanying drawing, in which'the single figure is a diagrammatic view of a tension control system embodying my invention.

Referring now to the drawing, the control system shown comprises a pair. of roll stands Ill and II through which a strip of material I2, suchas sheet steel, is passed. The roll stands in and l I may be driven in any suitable manner, 40 as by means of motors I3 and M, respectively, which are connected to their respective roll members through gear sets l5 and I6.

The roll motors I3 and M are provided with armature windings l1 and I8 and separately ex- 45 cited fields windings l9 and 20 respectively. The armature windings may be energized from any suitable source of direct current power (not shown) through conductors 2| and 22, the motors l3 and I4 being connected thereto by con- 50 trollers 23 and 24, respectively. The separately excited field windings l9 and 20 are energized from power conductors 25 and 26, as will be explained more fully hereinafter.

In order to provide for maintaining a rede- 55 termined tension on the material l2, there is utilized a tensioning device for exerting a trans-' verse deflecting force on the material between the roll stands Ill and N. If a deflecting force is applied to the material l2 midway between the two stands, so as to move it from the plane of the straight pass line extending between the roll stands to a deflected position, the tension on the material will be a function of the sine of the angle of deflection alpha and the tension will remain substantially constant so long as the strip is maintained in this position under a constant force.

However, if the length of the material between the roll stands increases and the same constant deflecting force is applied, the angle of deflection becomes greater and, therefore, the tension on the material is reduced. The opposite is true in the event that the length of the material between the roll stands decreases, thereby causing the tension on the material to increase.

In view of the foregoing, it will be understood that in order to maintain a predetermined tension on the material, provision must be made for not only maintaining the tensioning means, which applies the force to the material, as nearly as possible in a certain position, but provision must also be made for causing a variation to occur in the amount of force produced by the tensioning means, depending upon the degree of deflection of the material from its normal path of travel. In general, the pressure characteristic must be such that the pressure increases with increasing height of the material above the pass line.

- In the present invention, this result is accomplished by utilizing a tensioning device which comprises an idler roller 3| mounted on one end of a bell crank lever 32 and a fluid pressure operated piston 33 which is disposed in a cylinder 34 and so connected to the other end of the bell crank lever 32 that the roller 3| is forced against the material l2. The bell crank lever 32 is pivotally mounted at 35 in order that the piston 33 may be-utilized to force the roller 3| upwardly against the material.

In order to maintain a predetermined tension on the material, the pressure in the cylinder 34 is regulated by means of a regulating valve 36, which is utilized to so vary the pressure ratio from inlet to outlet that, with a constant inlet pressure, a varying outlet pressure may be obtained. The outlet of the regulating valve 36 is connected to the cylinder 34 by means of a pipe 31 and the inlet of the valve may be connected to an air pressure tank 38, as shown. If desired, other suitable working mediums, such as any other gasor liquid, may be utilized in place of air.

The regulating valve 36 comprises a body 4| provided with an inlet opening 42 and an outlet opening 43, which may be connected respectively to the supply reservoir 38 and the line 31 leading to the fluid-pressure operated piston 33. The body 4| is provided with a spring cover 44 that houses a compression spring 45, the compression of which may be varied by means of a plunger 46. As shown, the spring 45 is disposed to control the position of a diaphragm 41 which, in turn, controls the operation of a valve 48.

In the present structure, the spring 45 is so constructed that the maximum pressure applied to the diaphragm 41 is sufficient to provide the maximum pressure required in the cylinder 34 and the plunger 46 is disposed to counteract the pressure of the spring 45. Air is admitted through the inlet opening 42, past the valve 48 until the pressure within the body 4|, which is applied to the diaphragm 41, is sufflcient to overcome the compressive force of the spring 45. The diaphragm 41 is then moved downwardly sufiiciently to permit a spring 49 to close the valve 48, thereby preventing the further flow of air through the inlet opening 42,

When the pressure within the body decreases to a value which is insufiicient to maintain the diaphragm 41 in a position to permit the valve 48 to remain closed, the valve is opened slightly to permit air to flow through the inlet opening to increase the pressure in the body of the valve and in the cylinder 34. Thus, it'will be seen that the outlet pressure may be regulated by varying the compression of the spring 45. If the spring pressure on the diaphragm 41 is increased, the outlet pressure increases and vice versa.

In order to provide for readily adjusting the valve 36 to vary the pressure maintained in the cylinder 34, an electrically energized solenoid is connected to the plunger 46. The solenoid 5| may be energized from the power conductors 25 and 26, or from any other suitable source, and the current flowing through the coil of the solenoid may be controlled by means of a manually operated rheostat 52 or by means of a regulator of the vibrating or other suitable type. In this manner, the operator can readily change the pressure in the cylinder 34, thereby controllin the tension on the material l2 to maintain a constant gauge of material or in case it is desired to change the gauge, this may be accomplished within certain limits by increasing or decreasing the tension, as the case may be.

In order that the tensioning device may inherently function to maintain the tension substantially constant over a certain range of operation or deflection of the material l2, the arm 32, which carries the roller 3|, should be positioned at an angle of approximately 51 from the plane through the pivot 35 parallel to the normal pass line of the'material. This arrangement or design causesthe tensioning device to be self compen-.

sating over a maximum range of operation and permits a limited amount of movement of the roller 3| resulting from variations in the length of the material between he roll stands without appreciably changing the tension on the material so long as the pressure provided on the bell crank lever by the piston 33 is substantially constant. The transverse or deflecting force exerted upon the material by the roller 25 is thereby automatically varied in accordance with the position of the roller in such manner as to maintain the material under substantially constant tension.

It is apparent that when the roller 3| moves upwardly, which requires a greater vertical or transverse forcein order to maintain the tension substantially constant, the distance between the vertical planesextending between the pivot point 35 and the center of the roller 3| is decreased, which causes an increase in the deflecting force. Likewise, when the roller 3| is depressed to a position below normal, the distance. between these same two points is increased, which correspondingly reduces the deflecting force in such proportion as to' maintain a substantially constant tension.

While the tensioning device herein described will satisfactorily maintain the tension over a wide operating range, it is desirable to make provision for constantly maintaining the tensioning device in as near a predetermined operating position as possible. f This may be accomplished by controlling the speed of at least one of the roll stand motors in accordance with the vertical movements of the tension roller 3| in such a manner that should the deflection of the material vary from a value considered as normal, the speed of at least one of the motors is varied in order to take up, the excess length in the strip of material or to increase its length, as the case may be.

As shown, provision is madefor automatically controlling the speed of the motor |3 by means of a regulator device 54, the functioning of which is caused to be influenced in accordance with the position of the roller 3|. As stated hereinbefore, the separately excited fleldwindings l9 and 20 of the motors l3 and M; respectively, are. energized from the power conductors 25 and 26. The field circuit of the motor I4 is provided with a variable resistance 55, which may be utilized to adjust the speed of the roll stand I Likewise,

the motor I3 is provided with a field rheostat 56 regulatorof any suitable type maybe utilized.

' contact element 61.

The vibrating contact element 62 is operated in a well known manner by means of an electromagnet 63 and an auxiliary relay 64. When the power conductors 25 and 26 areenergized, the electromagnet 63 is energized and raises the contact element 62 to its uppermost position. The energizing circuit for the electromagnet 63 contains a resistor 65 which is shunted by the auxiliary relay 64. Upon the operation of the electromagnet 63, its contact members 66 are closed to energize the auxiliary relay 64 which opens its contact members to insert the resistor 65 in the circuit for the electromagnet 63. This increases the resistance of the circuit for the electromagnet 63 to such an extent that the vibrating contact element. 62 is returned to its lowermost position. This cycle of operation is repeated thereby causing the contact element 62 to vibrate.

The regulator 54 is provided with an adjustable contact element 61 having upper and lower contacts which are positioned in any suitable manner in accordance with the position of the roller 3|. As shown, the contact element 67 is directly connected to the bell crank lever 32 by an arm 68 to transmit the motion of the roller 3| to the In order to more clearly describe the functioning of the regulator 54 to control the speed of the motor 3 in accordance with the movements of the roller 3|, it will be assumed that. the

-material 2 is traveling in the direction indi- I shunting relay 6| is energized to remove a shunt connection from the field resistor 58', thereby decreasing the excitation of the motor l3 and increasing its speed accordingly. When the contact element 62 is in its upper position, the shunt- Of time.

ing relay 59 is energized to shunt the resistor 51' from a fleld circuit thereby increasing the excitation of the motor which causes its speed to decrease.

The regulator 54 is so disposed that when thetension roller 3| is in its normal operating position, the vibrating contact element 62. makes contact with the upper and lower contacts of the adjustable contact element 61 for equal periods If, however, the deflection in the material [2 increases, the adjustable contact element '61 of the regulator'54 is so positioned that the vibrating element 62 engages the lower contact-of the contact element 61 for a greater time than it engages the upper contact, thereby causing the shunting-switch 6| to be maintained in its open position overlonger periodsoftime than the creases below its normal value, thereby causing the shunting switch 59 to be maintained energized over longer periods of time than the switch 6|. In this manner, the speed of the motor is decreased and the deflection of the material l2 increased.

In order toprovide for controlling the position of the roller 3| when it is not inengagement with a sheet of material, a hydraulic device 1| may be utilized to function as a stop for the lever arm 32. The device 1| comprises a piston 12 disposed in a cylinder 13 which also contains a spring 14 disposed to raise the piston 12 to lower the roller 3| when it is desired to start a new sheet ofmaterial through the roll'stands I0 and II. The piston 12 may be lowered by a pressure fluid under the control of valves 15 and 16 while the tensioning device is in operation.

From the foregoing description, it is apparent that I have provided a tensioning device which,

on account of its facility for readily changing the applied pressure, permits the operator to control not only the tension but also the gaugeof the material very closely. Thus, if the gauge of the material should decrease, the operator may readily decrease the pressure, thereby causing the gauge to increase, or if the gauge increases, the operator can increase the pressure, and thereby the tension on the material,- to maintain the desired gauge.

Since numerous changes may be made in the above described construction and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is 1. In a tension control system, in combination,

' a movable tensioning roller, fluid-pressure oper-' ated means for actuating said roller, means for regulating'the amount of fluid pressure on said fluid-pressure operated means, and electrically energized means for governing the operation of said regulating means to control the operation of the tensioning roller.

2. In a tension control system, in combination, a movable tensioning roller, fluid-pressure operated means for actuating said roller, means for regulating the amount of fluid pressure on said fluid-pressure operated means, electrically energized means for governing the operation of said regulating means to control the operation of the tensioning roller, and means for controlling the current in said electrically energized means.

3. In 'a tension control system, in combination, a movable tensioning roller, fluid-pressure operated means for actuating said roller, means for regulating the amountof fluid pressure on said fluid-pressure operated means, electrically energized means for governing the operation of said regulating means to control the operation of the tensioning roller, and manually operable means for controlling the current in said electrically energized means.

4. In a tension control system, in combination, a movable tensioning roller, fluid-pressure operated means for actuating 'said roller, means for regulating the amount of fluid pressure on said fluid-pressure operated means, a solenoid magnet for governing the operation of said regulating means, means for energizing said solenoid magnet, and means for controlling the energization of said solenoid to control the operation of said tensioning roller.

5. In a system for controlling the tension on a strip of material, in combination, an idler roller, a lever mechanism for forcing said roller against the material, fluid-pressure operated means for actuating said lever mechanism, means for regulating the amount. of fluid pressure on said fluid-pressure operated means, and electrically energized means for governing the operation of said regulating means to control the tension on said material.

6. In a system for controlling the tension on a strip of material, in combination, an idler roller, a lever mechanism forforcing said roller against the material, fluid-pressure operated means for actuating said lever mechanism, means for regulating the amount of fluid pressure on said fluid-pressure operated means, electrically energized means for governing the operation of said regulating means to control the tension on said material, and means for controlling the current in said electrically energized means.

7. In a system for controlling the tension on a strip of material, in combination, a bell-crank lever, an idler roller mounted on one end of said lever, a fluid-pressure operated piston disposed at the other end of said lever to force said roller against the material, a pressure regulating valve for regulating the amount of fluid pressure on said piston, electrically energized meansdor adjusting said regulating valve, and means for controlling the energizatidn of said electrically energized means to change the pressure on said piston, thereby controlling the tension on said material.

8. In a system for maintaining a predetermined tension on a length of material extending bethe transverse force in accordance with its oper-.

ating position between predetermined limits to subject the material to a substantially constant tension, and means responsive to the operation of the tensioning means for controlling the operation of the speed controlling means, thereby to maintain such relative speeds of the roll stands as will hold the tensioning device within its predetermined operating limits.

9. In combination, a plurality of spaced work devices for simultaneously working a piece of material extending therebetween, a motor for actuating each work device, self compensating pressure fluid actuated means for exerting a transverse thrust upon the material so constructed and disposed as to subject said material to a substantially constant tension and deflect it from its normal pass line between the work devices, and means including a voltage regulator responsive to the movements of said thrust exerting means for controlling the excitation of at least one of said motors, thereby to maintain a substantially constant length and deflection of the material between the work devices.

10. In combination, a plurality of spaced work devices disposed to simultaneously work a piece of material extending therebetween, a pressure fluid actuated device positioned between the work devices disposed to subject the material to a transverse thrust to deflect the material from its normal path of travel and thus tension the material, said device being so constructed and disposed as to be self-compensating thereby to subject the strip to predetermined tensions over a predetermined range of movement, and regulator means controlled in accordance with the position of the pressure fluid actuated device within said predetermined range of movement for controlling the speed of at least one of said work devices, whereby the length of material and degree of deflection thereof between the work devices is controlled to maintain the pressure fluid actuated device in a predetermined position.

11.'In combination, a plurality of spaced roll stands for simultaneously rolling a piece of material extending therethrough, means for driving the roll stands, means including a pressure fluid actuated roller positioned intermediate the roll stands for subjecting the material to a transverse force to thereby tension it, said means being so constructed and disposed as to so vary the transverse iorce as to Subject the material to a substantially contant tension over a predetermined range of movement of the roller and angular displacement of the material from its normal path of travel by said roller, means for varying the speed of one of the means for driving the roll stands, and a regulator controlled in accordance with the position of the pressure fluid actuated roller within said predetermined range of movement for controlling the speed varying means, whereby the length of material extending between said roll stands and the degree of deflection thereof are so controlled as to maintain said roller within the predetermined range ofmovement.

12. In combination, a plurality of work devices arranged in spaced relation for simultaneously working a piece of material extending therebetween, means for driving each work device, a pressure fluid actuated pressure roller disposed between the work devices for exerting a transverse deflecting force upon the material to tension the material and cause it to move in an angular path with respect to its' normal path of travel, said pressure roller having a predetermined operating range and being so constructed and disposed as to automatically function within said predetermined operating range to vary the force exerted upon the material in proportion to its degree of angular deflection, and means controlled by said pressure fluid actuated pressure roller for controlling the speed of at least one of the driving means to control the length of the material between r011 stands and consequently the degree of angular deflection to maintain the pressure fluid-actuated pressure roller within its predetermined operating range.

13. In combination with metal working devices adapted for simultaneous operation on a strip of material passing therethrough under tension; of tensioning means positioned intermediate the work devioes ior subjecting the material to a I transverse force deflecting the material out of its normal straight-line path of travel, said means comprising a pivotally mounted pressure fluid actuated bell crank lever device having a pressure roller disposed to engage the material mounted on one arm thereof, the arms of the bell crank being so disposed in such a predetermined angular relationship as to causethe transverse 5 deflecting force exerted by the pressure roller to be automatically varied in accordance with the degree of deflection of the strip to maintain a substantially constant tension thereon throughout a predetermined range of deflection. 1.

GERHARD LESSMANN. 

